Lifter Preload? How to measure? I don't get it.
03-31-2013, 03:06 PM
#1
On The Tree
Thread Starter
Join Date: Apr 2009
Posts: 103
Likes: 0
Received 0 Likes
on
0 Posts
Lifter Preload? How to measure? I don't get it. Hello all. I got some push rods that are way too long, when I tightened down the rockers it actually opened all the valves.
Anyways, so I need to try and measure for the right push rod length, but I can't figure out this whole lifter preload bit.
From the pictures I see, the lifter preload is when the lifter is pumped up, and you push it down .0X.
How do you measure that?? Every time I put the push rod in, it instantly bottoms out the lifter. (The lifter might not even be coming back up at all. I took a stock lifter that I had laying around and unless I put air through the hole it stays down.)
Is there a way to measure from where it bottoms out and subtract that from the length of the push rod to get the preload? Or does it not work like that?
Thanks.
Anyways, so I need to try and measure for the right push rod length, but I can't figure out this whole lifter preload bit.
From the pictures I see, the lifter preload is when the lifter is pumped up, and you push it down .0X.
How do you measure that?? Every time I put the push rod in, it instantly bottoms out the lifter. (The lifter might not even be coming back up at all. I took a stock lifter that I had laying around and unless I put air through the hole it stays down.)
Is there a way to measure from where it bottoms out and subtract that from the length of the push rod to get the preload? Or does it not work like that?
Thanks.
03-31-2013, 07:32 PM
#3
there's several ways to do it...either way you need to prevent from loading up the lifter during measurement which would give you a false reading.
I converted a couple of my old lifters to "solid lifters" by shimming them internally so they can't be compressed under load like so. Two (2) m4 washers + one (1) m6x12mm bolt does the trick (on ls1 stock lifters anyway). I secured it all with a snap ring because I lost the original spring retainer.
Then using lightweight valve-checking springs, you can use a pushrod length checker and set it for 0 lash with the rocker arm tight. I would not use a length checker with real valve springs because they would likely deflect your length checker. Determine this measurement required to achieve zero lash, and then simply add your desired preload value to it.
One other thing is to keep in mind what gasket thickness you use for the test and what you'll be running during the rebuild, if they're not the same then that will change the length you require.
I converted a couple of my old lifters to "solid lifters" by shimming them internally so they can't be compressed under load like so. Two (2) m4 washers + one (1) m6x12mm bolt does the trick (on ls1 stock lifters anyway). I secured it all with a snap ring because I lost the original spring retainer.
Then using lightweight valve-checking springs, you can use a pushrod length checker and set it for 0 lash with the rocker arm tight. I would not use a length checker with real valve springs because they would likely deflect your length checker. Determine this measurement required to achieve zero lash, and then simply add your desired preload value to it.
One other thing is to keep in mind what gasket thickness you use for the test and what you'll be running during the rebuild, if they're not the same then that will change the length you require.
03-31-2013, 07:58 PM
#4
On The Tree
Thread Starter
Join Date: Apr 2009
Posts: 103
Likes: 0
Received 0 Likes
on
0 Posts
Allllrrriiiggghhhttt, well I have had my heads torqued down for couple weeks now, and had intake and everything on, before I turned it over and noticed it had no compression. Looks like I need to take it all apart again?
I still don't quite understand.... how people measure the actual preload? They have to pump up the lifters right?
There is no other way? Do the manufacturers have the bottom on length and the filled length? Should be able to find the difference and find the preload from the bottom to get the correct length pushrod?
I still don't quite understand.... how people measure the actual preload? They have to pump up the lifters right?
There is no other way? Do the manufacturers have the bottom on length and the filled length? Should be able to find the difference and find the preload from the bottom to get the correct length pushrod?
03-31-2013, 08:15 PM
#5
You have to check as described. Lifters have a range, and you should aim for the middle of that range. Until you know the pushrod length at 0 lash, you have no idea where you'd be in relation to the preload range.
What lifters? What are the specs of heads, cam (lobes and core), valves, head gasket? I can probably give you a ballpark knowing those things that you could compare to the measurement.
What lifters? What are the specs of heads, cam (lobes and core), valves, head gasket? I can probably give you a ballpark knowing those things that you could compare to the measurement.
03-31-2013, 08:30 PM
#6
On The Tree
Thread Starter
Join Date: Apr 2009
Posts: 103
Likes: 0
Received 0 Likes
on
0 Posts
Lunati "High RPM" Lifters 72532
Trick flow 220 as cast, milled to 61cc
Cam is I think 236/238
Valves are 2.040 in. intake and 1.575 in. exhaust
Head gasket is 3 layer GM Multi Layer Steel OEM Head Gasket.
Rods I got are 7.5 and they are WAY too long, not even semi close. Valves are open huge. Put the stock 7.4s in one today to see that and they are also too large, opens the valve.
I guess I just don't understand, I put the push rod in, and the lifter is already bottomed out... how can you possibly measure preload with the lifter bottomed out? Like I said I looked at my stock ls1 lifter and it also doesn't seem to have a spring in it that pushes the lifter plunger up when it is empty of oil. I am very confused.
Here is the example of instructions I have seen everywhere:
make sure your on the base circle
using a know length pushrod tighten to zero lash (rock becomes stable)
Take your torque wrench that is set to 22lb-ft and torque the 8mm bolt
Count the number of turns it takes to acheive 22lb-ft....1 full turn is worth .047"
Adjust the pushrod length accordingly for the desired preload
Does that assume the lifter is pumped up and the plunger is not going down?
Trick flow 220 as cast, milled to 61cc
Cam is I think 236/238
Valves are 2.040 in. intake and 1.575 in. exhaust
Head gasket is 3 layer GM Multi Layer Steel OEM Head Gasket.
Rods I got are 7.5 and they are WAY too long, not even semi close. Valves are open huge. Put the stock 7.4s in one today to see that and they are also too large, opens the valve.
I guess I just don't understand, I put the push rod in, and the lifter is already bottomed out... how can you possibly measure preload with the lifter bottomed out? Like I said I looked at my stock ls1 lifter and it also doesn't seem to have a spring in it that pushes the lifter plunger up when it is empty of oil. I am very confused.
Here is the example of instructions I have seen everywhere:
make sure your on the base circle
using a know length pushrod tighten to zero lash (rock becomes stable)
Take your torque wrench that is set to 22lb-ft and torque the 8mm bolt
Count the number of turns it takes to acheive 22lb-ft....1 full turn is worth .047"
Adjust the pushrod length accordingly for the desired preload
Does that assume the lifter is pumped up and the plunger is not going down?
Trending Topics
03-31-2013, 09:31 PM
#8
On The Tree
Thread Starter
Join Date: Apr 2009
Posts: 103
Likes: 0
Received 0 Likes
on
0 Posts
03-31-2013, 09:38 PM
#9
the lifter cups are spring loaded, so you shouldn't have to pump them up. Just be carfull when finding zero lash (on the base circle of the cam) not to push the cup down.
03-31-2013, 09:54 PM
#14
TECH Fanatic
iTrader: (7)
Here's a link to a thread with a guy running the same lifters as you...
I know his cam is probably different...but there is some info here.
Lunati/Morel 72532 Lifters
I know his cam is probably different...but there is some info here.
Lunati/Morel 72532 Lifters
03-31-2013, 10:03 PM
#15
On The Tree
Thread Starter
Join Date: Apr 2009
Posts: 103
Likes: 0
Received 0 Likes
on
0 Posts
Wouldn't the lifters close before the dual springs compressed and the valve opened? (I'm just guessing, I don't know.) Also I have turned the motor over with the starter, that can't be enough oil pressure to pump up the lifters can it?
03-31-2013, 10:07 PM
#16
On The Tree
Thread Starter
Join Date: Apr 2009
Posts: 103
Likes: 0
Received 0 Likes
on
0 Posts
Here's a link to a thread with a guy running the same lifters as you...
I know his cam is probably different...but there is some info here.
Lunati/Morel 72532 Lifters
I know his cam is probably different...but there is some info here.
Lunati/Morel 72532 Lifters
03-31-2013, 10:11 PM
#17
if you were cranking it continuously for seconds at a time, yes that would create pressure
03-31-2013, 10:22 PM
#19
You need to measure with a SOLID lifter. Shim up an old one as I described to bring the pushrod cup to the top of its travel. At this point the lifter is imcompressible. From there you set your push-rod length checker to zero lash (0 preload). Your desired pushrod length is the length of the checker at this zero lash value, + your desired preload. When you install your actual lifters that have push-rod cups with available travel, you will get the preload you need. Trying to "pump one up" for measuring would be pretty unreliable when you're trying to hit what is likely a 0.030"-0.060" window.
03-31-2013, 10:23 PM
#20
Why are you running the Morel 5294s in a street motor? I would advise against that. If you get any kind of particle of dirt in the oil and it makes it into that lifter. It'll seize up. Erik @ HKE recommends the 5206 on a street application, because of that.
Now, 7.5" would be fine with an LS7 lifter in that motor. Since the Morel/Lunati lifter needs less preload ~ .030-.050" less (depending on where the stock LS7 lifter would be with the 7.5") and has a .050" taller body/cup, you need at least a .100" shorter pushrod or maybe only a .080" shorter. But you also have a smaller base circle cam, so that adds back .025" and a milled head, so that's about .020" closer. In any event, .100" would get you a lot closer, but still might be off for the preload a good .020-.040" which would be bad with a lifter that has a pretty narrow window (.030"-.050" preload). Without measuring, you can't tell and are going to destroy some high dollar parts.
Now, 7.5" would be fine with an LS7 lifter in that motor. Since the Morel/Lunati lifter needs less preload ~ .030-.050" less (depending on where the stock LS7 lifter would be with the 7.5") and has a .050" taller body/cup, you need at least a .100" shorter pushrod or maybe only a .080" shorter. But you also have a smaller base circle cam, so that adds back .025" and a milled head, so that's about .020" closer. In any event, .100" would get you a lot closer, but still might be off for the preload a good .020-.040" which would be bad with a lifter that has a pretty narrow window (.030"-.050" preload). Without measuring, you can't tell and are going to destroy some high dollar parts.